Introduction to PHP

Introduction to PHP

“PHP is a server-side scripting language designed specifically for the Web. Within an

HTML page, you can embed PHP code that will be executed each time the page is visited.

Your PHP code is interpreted at the Web server and generates HTML or other output that the

visitor will see” (“PHP and MySQL Web Development”, Luke Welling and Laura

Thomson, SAMS)

Introduction to PHP PHP Hypertext Preprocessor.

Other Names : Personal Home Page, Professional Home Page

Is a server side scripting language. Capable of generating the HTML pages

HTML generates the web page with the static text and images.

However the need evolved for dynamic web based application, mostly involving database usage.

CLIENT

WEB SERVER

HTTP Request(url)

<HTML><?php PHP code ?></HTML>

Gets Page

<HTML><B>Hello</B></HTML>

Interprets the PHP codeServer response

Browser createsthe web page

Hello

Why PHP? ..there are no. of server side scripting available

like ASP, SSJS, JSP….. PHP involves

simplicity in scripting (..generally using the database)

platform independence. PHP is

primarily designed for web applications well optimized for the response times needed for

web applications Is an open source.

PHP Block PHP code block is embedded within the <?

php and ?> tags. When the server encounters the PHP tags

it switches from the HTML to PHP mode. There are four different ways to embed the

PHP code <?php echo(“Some PHP code”); ?> <? echo(“Some PHP code”); ?> <SCRIPT Language=‘php’> echo(“Some PHP code”);

</SCRIPT> <% echo(“Some PHP code”); %>

Hello World! (web oriented)

<html><head> <title>My personal Hello World! PHP script</title></head><body><?echo “Hello World!”;

?></html>

PHP tag, allow to insert PHP code. Interpretation by PHP module will substitute the code with code output

Variables (I)

To use or assign variable $ must be present before the name of the variable

The assign operator is '='

There is no need to declare the type of the variable

the current stored value produces an implicit type-casting of the variable.

A variable can be used before to be assigned

$A = 1;

$B = “2”;

$C = ($A + $B); // Integer sum

$D = $A . $B; // String concatenation

echo $C; // prints 3

echo $D;// prints 12

Variables (II)

Function isset tests if a variable is assigned or not$A = 1;

if (isset($A))

print “A isset”

if (!isset($B))

print “B is NOT set”;

Using $$$help = “hiddenVar”;

$$help = “hidden Value”;

echo $$help; // prints hidden Value

$$help = 10;

$help = $$help * $$help;

echo $help; // print 100

PHP Variables (cont.) Rich set of functions for working with

variable. For e.g

gettype, settype, isset, unset, is_int, intval etc etc

Strings (I)

A string is a sequence of chars

$stringTest = “this is a sequence of chars”;

echo $stringTest[0]; output: t

echo $stringTest; output: this is a sequence of chars

A single quoted strings is displayed “as-is”

$age = 37;

$stringTest = 'I am $age years old'; // output: I am $age years old

$stringTest = “I am $age years old”; // output: I am 37 years old

Concatenation

$conc = ”is “.”a “.”composed “.”string”;

echo $conc; // output: is a composed string

$newConc = 'Also $conc '.$conc;

echo $newConc; // output: Also $conc is a composed string

Arrays (I)

Groups a set of variables, every element stored into an array as an associated key (index to retrieve the element)$books = array( 0=>”php manual”,1=>”perl manual”,2=>”C manual”);

$books = array( 0=>”php manual”,”perl manual”,”C manual”);

$books = array (“php manual”,”perl manual”,”C manual”);

echo $books[2]; output: C manual

Arrays with PHP are associative$books = array( “php manual”=>1,”perl manual”=>1,”C manual”=>1); // HASH

echo $books[“perl manual”]; output: 1

$books[“lisp manual”] = 1; // Add a new element

Arrays (II)Working on an arrays

$books = array( ”php manual”,”perl manual”,”C manual”);

Common loop

for ($i=0; $i < count($books); $i++)

print ($i+1).”-st book of my library: $books[$i]”;

each

$books = array( “php manual”=>1,”perl manual”=>2,”C manual”=>3);

while ($item = each( $books )) // Retrieve items one by one

print $item[“value”].”-st book of my library: ”.$item[“key”];

// each retrieve an array of two elements with key and value of current element

each and list

while ( list($value,$key) = each( $books ))

print “$value-st book of my library: $key”;

// list collect the two element retrieved by each and store them in two different // variables

Arrays (II)

each and list

while ( list($value,$key) = each( $books ))

print “$value-st book of my library: $key”;

// list collect the two element retrieved by each and store them in two different // variables

Arrays (III)Multidimensional arrays

$books = array( array(“title”=>“php manual”,”editor”=>”X”,”author”=>”A”),

array(“title”=>“perl manual”,”editor”=>”Y”,”author”=>”B”),

array(“title=>“C manual”,”editor”=>”Z”,author=>”C”));

Common loop

for ($i=0; $i < count($books); $i++ )

print “$i-st book, title: ”.$books[$i][“title”].” author: “.$books[$i][“author”].

“ editor: “.$books[$i][“editor”];

// Add .”\n” for text new page or “.<BR>” for HTML new page;

Use list and each

for ($i=0; $i < count($books); $i++)

{

print “$i-st book is: “;

while ( list($key,$value) = each( $books[$i] ))

print “$key: $value ”;

print “<BR>”; // or “\n”

}

Arrays (cont.) $ncststaff = array (“dake” => array(“amrish”, “lakshana”,

“venkat”),“spc” =>

array(“narayan”, “murali”,“prasad”));

creates a two dimensional array. Sorting Functions

sort() : sorts the elements in the numeric and alphabetical order.

rsort() : sorts the elements in the reverse order. asort() : sorts the elements in the array without

changing the indices. ksort() : sorts the arrays by key.

PHP Statements IF statement

if (<condition>) {//php code goes here}

else {//php code goes here}

Alternative Syntaxif(<condition>) :

//html code goes hereelse :

//html code goes hereendif;

PHP Statements (cont.)

For loopfor($i=0;$i < 10;$++i) {

echo(“the value is :”. $i);

} Alternative Syntax

for($i=0;$i < 10;$++i) :// html code goes here

endfor; While loop Do-While loop

Introduction to PHP

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